Fixing bleaching-out pictures



Patented Mar. 22, 1932 UNITED STATES PATENT- OFFICE BRUNO WENDT, OF DESSAU IN ANHALT, AND HANS BINCER, F DE SSAU-ZIEBIGK 1N ANHAL'I', GERMANY, ASSIGNORS TO AGFA ANSGO CORPORATION, OF BINGHAMTON, NEW YORK, A CORPORATION OF NEW YORK rrxme BLEAcHme-oUr PICTURES.

No Drawing. Application filed April 25, 1930, Serial No. 447,420, and in Germany May 11, 1929.

Our present invention relates to a process 5 dimin shed by removing the sensitizer from the picture. This operation has, however,

. been difiicult since the solvents for the sensitizer also attack the dyes constituting thepicture. 0

According to this invention, for fixing such bleaching-out layers sulfurous acid is used with good result. It acts upon the derivative of thiourea serving as sensitizer without'exerting any injurious influence on the dye.

The sulfurous acid may be used either in aqueous solution or dissolved in an organic solvent. The solvent selected for this purpose must be one which does not act upon the binding agent in the layer to be fixed in each of bleaching out dyes constituting the picture a mechanical way or by means of an indifferent liquid, for instance, benzene.

The following example serves to illustrate the invention:

about 3 hours in a closed vessel on the bottom of which there is a dish charged with an aqueous solution of sodium bisulfite. On the layer a decomposition product of the sensitizer, which is of unknown constitution segregates in the form of oily drops which are removed by means of a piece of'fabric moistened with benzene.

The invention'is not limited to the foregoing example or to the specific details given therein. Thus, for instance, instead of an aqueous solution of sodium bisulfite a solution of sulfurous acid in a suitable solvent evolving gaseous sulfur dioxide may be used. Or, the unfixed icture may be treated in a bath containing in the case of nitrocellulose used as a binding agent for the dye a mixture of benezene and methyl alcoholin the ratio 4: 1 and sulfurous acid in a quantity up to saturation. Thus, the fixing process is finished in about 20 minutes.

In the same manner, other layers containa ing other sensitizers of the group comprising derivatives of thiourea, may be fixed.

What we claim is 1. The process of fixing bleaching-out layers containing a derivative of thiourea as a sensitizer, which comprises acting upon said layer which sulfurous acid.

2. The process of fixing bleaching-out layers containing a derivative of thiourea as a sensitizer, which comprises acting upon said layer with gaseous sulfur dioxide.

3. The process of fixing bleaching-out layers containing allylthiourea 'as a sensitizer, which comprises acting upon said layer with sulfurous acid.

4. The process of fixing bleaching-out layers containing allylthiourea as a sensitizer, whichcomprises acting upon said layer with gaseous sulfur dioxide.

In testimony whereof, we affix our signatures.

' BRUNO WENDT.

HANS BINCER.

A picture made by the bleaching-out process the binding agent of which consists of nitrocellulose and which contains diethylallylthiourea as a sensitizer, is placed for 

